1. Field of the Technology
The present disclosure relates generally to connection migration methods and apparatus between wireless local area networks (WLANs) and wireless wide area networks (WWANs) for communication devices such as mobile communication devices.
2. Description of the Related Art
The present disclosure relates generally to connection migration methods and apparatus between WLANs (e.g. IEEE 802.11 based networks) and WWANs (e.g. cellular telecommunication networks for communication devices such as mobile communication devices (e.g. wireless handsets or WHs). The specific problem addressed involves the support of real-time voice connections when multi-mode WHs are used in enterprise settings. Each WH has a WLAN radio interface and a cellular radio interface. When a voice connection is active through the WLAN interface and the WH roams out of WLAN coverage, the call is maintained by re-connecting it through the WH's cellular interface. The transition between these two interfaces and networks is referred to as a vertical handover (VHO). The switch between interfaces must be done subject to strict latency constraints, so that the voice connection quality is not adversely affected.
In order to enable VHO, the connection is normally split into two call “legs” which are anchored either in the cellular network (CN) or in the enterprise. The “anchor” is the point where the two call legs come together. When VHO occurs, one of these legs is replaced by a new call leg that is established through the wireless network (WLAN or cellular) to which the WH is handing-over. Enterprise anchoring (EA) is complex from a user's point of view since the handover must be anchored and managed by equipment inside the enterprise, such as a Public Switched Telephone Network (PSTN) gateway or IP Public Branch Exchange (PBX). Cellular network anchoring (CNA) pushes this complexity into the CN, which is more desirable from that point of view. CNA is often capable of much faster handovers since both WLAN and cellular call legs terminate inside the cellular operator's core network. The CNA model is typical of currently proposed carrier-based dual-mode device solutions such as IP Multimedia Subsystem (IMS) and Unlicensed Mobile Access (UMA). Enterprise anchoring normally incurs longer VHO execution delays than CNA because the new cellular call leg setup must propagate through the cellular core network, the PSTN, and the enterprise network.
Unfortunately, the user of CNA even requires that all intra-enterprise calls placed to/from WHs be routed through the CN when the call is made. This is required to establish the anchor needed in the event that a VHO occurs at some later time during the call. Thus, placing intra-enterprise calls is expected to be more costly since enterprise users will be billed by the cellular operator even for calls which remain internal to the enterprise. Enterprise customers who have invested in a telecom infrastructure and WLAN infrastructure that they manage may be reluctant to pay a carrier to use their own network. In addition, if all calls are forced to go through the CN, it will not be possible to fully utilize the enhanced capabilities that are available in the enterprise infrastructure.
Accordingly, there is a need for improved connection migration methods and apparatus to overcome the deficiencies of the prior art.